Reaction Dynamics in Extreme Environments - Boron Reactions Ralf I. Kaiser, University of Hawaii at Manoa (FA9550-09-1-0177 )

Reaction DynamicsWe have elucidated the energetics and dynamics of elementary reactions of ground state boron atoms (B(2Pj)) with simple nitrogen-bearing molecules: ammonia (NH3) and hydrogen cyanide (HCN). The closed shell molecules serve as prototype reaction partners to access the HxBCyN (x=0,1,2,3; y=0,1) potential energy surface which is important in the fields of basic physical chemis- try (reaction dynamics), combustion chemistry, material sciences, chemical propulsion systems, physical organic chemistry, and che- mical vapor deposition processes (boron-nitride films, ternary BCN compounds). The experiments are pooled together with electronic structure calculations (Bartlett et al.; Mebel et al.) to verify the elu- cidated reaction mechanisms theoretically; this ultimately bridges the understanding of reactive scattering processes involving small boron-bearing systems via quantum chemical methods and experi- ments.

HNBH

B. Jones et al., J. Phys. Chem. A 2010, 114, 8999–9006

F. Zhang et al., J. Phys. Chem. A, DOI: 10.1021/jp107210d

ResultsThe reaction of boron with hydrogen cyanide revealed that the boronisocyanide molecule, [BNC], is formed as the exclusive pro- duct under gas phase single collision conditions via indirect scatte- ring dynamics. The corresponding TOF spectra of the ionized parent molecule are depicted on the right. We also show that higher energy isomers such as the hitherto unnoticed, ring-strained cyclic BNC structure, which is isoelectronic to the triplet, cyclic tricarbon molecule, [C3], exist as local minima. Our study presents the first clean synthesis and observation of gas phase boron isocyanide providing a door way for further fundamental, spectroscopic stu- dies on one of the simplest triatomic molecules composed solely of group III – V elements. The data from our studies also help to understand the chemical synthesis of macroscopic amounts of BNC material on the industrial scale.

Reaction Dynamics in Extreme Environments - Polymers Ralf I. Kaiser, University of Hawaii at Manoa (FA9550-09-1-0177 )

Reaction DynamicsThis project investigates the effects of ionizing radiation with polymers (Kapton, Teflon, PE, PS, PMMA) utilizing a surface scattering machine. These experiments help to untangle the stability of polymers toward space weathering (cosmic rays, energetic electrons, ions, photons) at temperatures ranging from 10 K to 300 K to mimic the extreme conditions experienced in Low Earth Orbit and the surfaces of the moon and Mars. Here, we report on the interaction of energetic electrons as generated in the track of galactic cosmic ray par ticles with all five polymers in a UHV chamber (510-11 torr). The irradiated samples are analyzed via infrared and UVVIS spectroscopy; the gas phase is monitored via a quadrupole mass spectrometer. Mechanistical results on polymer degradation via chain rupture versus chain branching, molecular hydrogen, carbon monoxide, and carbon dioxide formation are discussed. Kinetic profiles of the newly formed molecular bonds are also presented. Successive experiments, done in collaboration with the Sibener Group in Chicago, will focus on the effects of singly ionized oxygen atoms with spin-coated polymer films (100 – 200 nm) in collaboration with Sibener et al..

C.P. Ennis & R.I. Kaiser Phys. Chem. Chem. Phys., 2010, 12,14884-14915